Post an MT message response to the client URL (if configured).
This callback is a vibes initiated request to the client to attempt delivery of carrier responses. The delivery of these messages is contingent on the client configuring the receiptOption tag on the original submission of the MT message. The client endpoint should properly store/record the response and then return an HttpResponse; 200 to acknowledge receipt. The client process should keep actual processing/logic as small as possible, for throughput and performance.